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On the Influence Coding Method on Japanese Speech Intelligibility in Virtual 3-D Audio Space

In this paper, we investigated the influence of stereo coding on the 3D audio for Japanese. We encoded localized test samples using joint stereo and parametric stereo of the HE-AAC encoder at identical coding rates. The Japanese word intelligibility test employed was the Japanese Diagnostic Rhyme Tests (JDRT). First, we localized the speaker in front of the listener at an arbitrary distance a (1.00a). Next, we compared the effect of noise located at a distance of 0.25a from the listener at one of the angles 15 degrees apart on the horizontal plane. The result showed that the target speech cannot be separated from the noise for any stereo coding when the noise was in front of speaker between azimuths of +30 deg. to -30 deg. However, at other azimuths, the intelligibility scores were far better. Stereo coding shows degraded intelligibility compared to the reference at any noise azimuths. However, joint stereo was shown to be constantly better compared to parametric coding, suggesting that the former is the stereo coding of choice for transmission of localized 3D audio.